Author here. My goal is to (eventually) host a toy key:value store on top of a unikernel. So the KV store would need to persist data to a writable file system. It's great when you don't need to alter state and the unikernel can be immutable (baking config into code ala Mirage, etc)...but something like a KV store can't get away with that.

But, the KV store + unikernel is mostly for fun, so may not be the most practical of real-world ideas anyway :)